Optical system for microscopes having a two-component objective



United States Patent 3,2d1,443 @PTICAL SYSTEM FR MICROSCUPES HAVING A IWU-CMPUNIIN'I' @BIECTIVE Harold E. Rosenberger, Erighton, N.Y., assigner to Bausch @t Lomb incorporated, Rochester, NSY., a corporation of New York Filed Dec. 26, 1962, Ser. No. 247,210 3 Claims. (Cl. 88-57) The present invention relates to a simple optical system for a microscope and more particularly it relates to improvements in such systems.

It is a prime object of this invention to provide a novel optical system of high magnification which is extremely simple in structure for low cost and is capable of unusually high-grade performance as judged by the excellent state of correction for chromatic and spherical aberrations, coma, and astigmatism.

A further object is to provide such a device which utilizes the least number of different lens curvatures together with plano surfaces to reduce the cost thereof and for the same purpose utilizes the same kind of glass in all collective elements.

Further objects and advantages will be found in the form and arrangement of the parts of the optical system and in the constructional details thereof from a study of the specification herebelow taken in connection with the accompanying drawing, in which:

FIG. 1 is an optical diagram showing the present invention; and

FIG. 2 is a chart of constructional data related to a preferred form of said invention.

As shown in the drawing, said optical system is generally designated by numeral 1I) and comprises a succession of four plano-convex lenses which are optically aligned with each other and are constructed so as to achieve a high numerical aperture of at least 0.12 and a magnification of substantially l00 Said optical system It) is furthermore so constructed as described herebelow that an unusually fine state of correction of chromatic and spherical aberrations is achieved as well as excellent correction of coma and astigmatism.

According to this invention, the optical system 10 features an ultimately simple and low-cost construction as set forth herebelow with particular reference to the character of the lens surfaces and properties of the lens materials.

Comprised in the optical system It) is a succession of four optically aligned plano-convex lenses which are designated I to IV progressively numbering from the front of the system. The plano sides of lenses I and II face forwardly toward entrant light while the plano sides of lenses III and IV face rearwardly, and an eyelens diaphragm Il is situated between the rearmost lenses III and IV. All of the lenses are singlets except lens II which is a doublet. Lens I is axially spaced rearwardly of a specimen surface l2 at a distance represented by S1 and together with lens II constitutes the objective portion of the system lll. Lens II is a doublet which is spaced at an axial distance designated S2 from lens I and is composed of a negative plano-concave element in contact on its rear side with a positive double convex lens element.

For costreducing reasons in the production of lenses I and II and for simplicity of the assembly operation in the doublet lens, all of the radii of the -lens curvatures of these lenses are substantially of the same numerical value.

The eyepiece section of the optical system 10 consists of the aforesaid lens III which is spaced at an axial distance designated S3 rearwardly of the doublet lens II,

3,241,443 Patented Mar. 22, 1966 ice and further consists of the lens IV which is separated from lens III by an axial distance designated S4. As aforementioned, the diaphragm 11 is provided in the plane of the image formed cooperatively by lenses I, II and III, and said diaphragm is located at an axial distance S5 forwardly of lens IV. The diameter of said diaphragm lll is substantially 12F where F represents the positive focal length formed cooperatively by lenses I and II.

In fulfillment of the objects of the present invention, the values of the optical parameters of the optical system 10 are specified in the table of mathematical statements herebelow wherein `the respective focal lengths relating to the lenses I to IV are represented by FI to FIV, R1 to R9 represent the successive radii of the lens surfaces on said lenses and lens elements, and the minus sign used with R2 and R5 applies to all lens radii which have a center of curvature located on the object or entrant side of the optical system with respect to the apex of the lens surface, t1 to t4 represent the axial thicknesses of the lenses I to IV, S1 to S5 represent the adjacent axial air spaces, and 11D and u represent the refractive index and Abbe number respectively of the lens material used in said lenses.

Furthermore, doublet lens II is composed of a front plano-concave lens element which is in Contact on its rear surface with a double convex lens element and the lastnamed element has an axial thickness of substantially .7512. With regard to focal lengths, the plano-concave lens element has a negative focal length of substantially 1.095F and the double convex element has `a positive focal length of substantially .78411.

Since the optical system It) is designed for the lowpriced market, all of the lens elements therein are very simple in form and construction to achieve minimum cost. To further reduce the cost of the constituent lens elements, each such element is manufactured in commercial quantities by an economical process wherein `a manufacturing tolerance is applied to each lens parameter thereof. Although a very exact approach to the precise nominal lens parameter values could be achieved by long and skillful grinding and polishing, such a practice is not feasible because of its excessive cost.

For practical reasons, therefore, commercially acceptable ranges of values are set forth in the preceding table of lens parameter values, said ranges being so chosen as to provide a multiplicity of modified but near-duplicate optical systems of the kind here disclosed, the lens parameters of each such optical system lying within the ranges given in the tables. Each such slightly dilferent or nonideal optical system is selectively assembled by skilled workmen from a great number of slightly dissimilar lenses having many non-standard lens parameter values within the stated ranges so that a degree of compensation of aberrations is achieved whereby the resulting optical perlens II being a doublet, lenses I and II having their plano sides facing toward the front and lenses III and IV having their plano sides facing rearwardly, ylens I being spaced at an object distance Si rearwardly of a specimen surface and jointly with lenses II and III forming an image of said specimen in a rearward eyepiece diaphragm, lenses I and II being separated by an axial distance designated S2, lenses l'I and III being separated by an air spiace designated S3, said lenses III and IV being separated by an air space designated S4, and said diaphragm being located at an axial distance designated S forwardly of lens IV, the constructional data for said system ybeing given in the talble of mathematical expressions herebelow wherein the air spaces Si to S5 are designated as hereformance is good and is commercially acceptable. Said l5 above FI to FIV designate @be focal `lengths of the non-standard lens parameter values may all lie unilaterally successive lenses I to IV, R1 to R9 designate the radii on the same side of nominal values in which case the 0f the Successive ,lens snnfas numbering from the optical result is closer to an ideal condition than a totally front of ,the system, .blib minus Sign used thererandom choice of parameter values within the specified Wipli being applied .tb any lens Surface having a center ranges. off curvature lying on the object side of the vertex The Values 0f Said Optical Parameters are more of tlhe surface, the thicknesses of the successive lenses SPeCiCaUY Set forth for one form 0f th@ Present IlVeH are designated ti to t4, the refractive index and Abbe tion in the table of mathematical statements herebelow number of the glass in `Said lenses being designated wherein the various parameters are designated in the same D and respectively, and the combined focal length manner as found in the above table. of lenses I to II being designated F,

F1=151F R8=132F 1.43F F1 1.58F F11=229F R9=w 2..18F F1I 2.41F Fm=3.71F 11:.187F 3.52F Fm 3.90F F1v=2.52F f2=250F 30 2.39F FW 2.55F R1= t3:'387F R1 i(Fr|"F1rlFrrrl-FIV) lR2=788F .749F -R2 .828F

:1:00 1=- R i(Fi F F F R4=788F S2=125F .749F Ri, .8281;L H+ 111+ IV) -R5=788F S3=987F 3, .749F R5 .828F R6=1-94F SP3-03F o 1.84F R6 2.04F R7= S5=2`52F R7 i(F1lFrrl-F1rrlrFrv) 1.25F R8 1.39F n., n R9 (F1+F1r+F1rrl-Frv) .178F ti .196F Lens I 1 .238F t2 .263F

n I .ee iii 1i iii sei-9 i ai if? 1- 524 59- 5 .784F Si .856F .119F S2 .131F One preferred form of the present invention is nurner- 9.3 8F S3 10.4F ircally specilied in the chart of values of the above-mern 12.88F S4 3.l8F tioned optical parameters as shown herebelow. 2.39F S5 2.65F

Magnflcaton=100 Numerical Aperture=0-l2 Lens Focal Length Rad Thick- Spaces nn n DGSSGS I F1 12.041 R1=m n =1.5 1.524 59.5

-Rz=6.3096 S1=6.6 Fn 18.341 R3=w t2 =2.0 Neg.=1.720 29.3 II {Neg.=s.763 R4=6.3095 Neg.=0.5 s2=1.0 l

Pos 6.277 -R1=0.3095 Pos. :1.5 s :790 Pos.=1.524 59.5 Fm 29.595 R=15.550 t, =3.1 3 1.524 59.5 III 7= S4=24-3 Frv 20.168 R=10.55s t1 =2.0 1.524 59.5 IV s5=20.2

Although only a preferred fonm of this invention has been shown and described in detail, other forms are pos- D l, sible and changes may be made in the optical parameters thereof within the above-stated ranges winhout departing Lensr 1.520 to 1.528 57.0 to 02.0 from the spirit of t1he invention as defined in the claims EEileen'fjjj ij il 51?, here apiended' fljjiijiiiiijii lig E3 I 23:3 i3 25:3

I claim: 1. An optical system for a microscope having a numerical aperture of .12 and a magnification of substantially and being corrected for chromatic and spherical aberration, coma and astigmatism, said system consisting of four optical-ly aligned plano-convex lenses numbered successively I to IV, lenses I, III `and IV being singlets and 75.

said doublet lens II being composed of a planoconcave lens element and a double convex lens element in contact with the rear surface thereof, the axial thickness of said double convex element being substantially .7512.

5 2. An optical system for a microscope having a numerical aperture of .12 and a magnification of substann, ,L tially 100 and being corrected for chromatic and sperical aberration, coma and astigmatism, said system conens% 524 sisting of four optically aligned plano-convex lenses num- 5 eus Se@ em' -720 ,j bered successively I to IV, lenses I, III and IV being if singlets and lens II being a doublet, lenses I and II hav- Lens IV M24 595 ing their plano sides facing toward the front and lenses III and IV having their plano sides facing rearwardly, said doublet lens II being composed of a planolens I being spaced at an object distance S1 rearwardly 1() concave lens element and a double convex lens of a specimen surface and jointly with lenses II and element being substantially .7512, and III forming an image of said specimen in a rearward of, the axial thickness of said double convex eyepiece diaphragm, lenses I and II being separated by element being substantial-ly .75z2, and an axial distance designated S2, lenses II and III being said diaphragm having a diameter of substanseparated by an air space designated S3, said lenses III 15 tially 1.2F. and IV being separated by an air space designated S4, 3- An Optical System for a rnicrOScOPe beVirlg e nu' and said diaphragm being located at an axial distance rnerical aperture 0f 1 2 and 2l magnification 0f substandesignad Sforwardly @flens 1V, tiallyl 100 and being corrected for. chromatic and the constructional data for said system being given in sphelal aberfauon @ma an@ astlgmalsm 'Sald System the table of mathematical expressions herebelow 2O conslstmg of fou optlcauy ahgned panoconvex lenlses wherein the air Spaces S1 to S5 are designated as numbered successively I to IV, lenses I, III and IV being hereabove, FI to FIV designate the ,focal lengths of singlets'and lens II being a doublet, lenses I and II havthe lenses I to IV, R1 to R9 designate the radii of mg the p 1an() .sldes @cmg towam the from and lenses the successive lens surfaces numfberinU from th fro t IH and IV having then: plano sldes facing rearwardly e e .n 25 lens I being spaced at an object distance S1 rearwardly Of,the Syst-em the mmus Slgn used therewlth of a specimen surface and jointly with lenses II and III bemg applied to any lens Surface havmg a Center forming an image of said specimen in a rearward eyeof curvature lying on the object side of the vertex piece diaphragm lenses I and H being Separated by an of the Surface the thlcknesses 0f the Successive axial space designated S2, lenses II and III being separated lenses are designated t1 to t4, the refractive index 30 by an air space designated S3, said lenses 1H and 1V and Abbe nurnber 0f tbe gieSS in Said lenses being being separated by an air space designated S4, and said designated "D and 1 respectively, 21nd the combined diaphragm being located at an axial distance designated focal length of lenses I and II being designated F, S5 forwardly of lens IV,

the constructional data for said system being given F 1 51F R 1 32P. 35 in the chart of numerical values herebelow wherein F :2 291: R :OO the air spaces AS1 to S5 are designated as hereabove,

H 9 F to F designate the focal lenoths of the lenses F :3.71F t=.187F I IV m 1 I to IV, R1 to R9 designate the radii of the succes- F1V:252F Z'Z'ZSOF sive lens surfaces numbering from the front 0f the Rlz t3:'387F 40 system, the minus sign used therewith being R2`2788F t4:'250F applied to any lens surface having a center of Curva- R3=00 S1:32517 ture lying on the object side of the vertex of the Rif-78817 S2=125F surface, the thicknesses of the successive lenses are "R5=788F Ss=9-87F designated t1 to t4, and the refractive index and Ris`=194F S4=303F 45 Abbe number of the glass in said lenses being desig- RT: S5=2.52F nated iiD and v respectively,

Magnitication=100 Numerical Aperture=0.12

Lens Focal Length Radii Thick- Spaces ILD v llGSSBS I Fi 12.041 Ri= ti =1.5 1.524 59.5

-R2=5.3095 S1=6.5 FII 18.341 Rs= t2 :2.0 Neg.=1.720 29.3 II {Neg.=8.763 R4=6.3096 Neg.=0.5 Sir-1.0

Pos.= 6.277 -R5=6.3096 Pos.=1.5 Pos.=1.524 59.5 Fin 29.695 Ri=15.5s0 n =3.1 S3-79'0 1.524 59.5 III 7= SF2-1.3

Fiv 20.168 R=10.568 t4 :2.0 1.524 59.5 IV 9= s5=2o.2

No references cited.

DAVID H. RUBIN, Primary Examiner.

JOHN K. CORBIN, Examiner.

R. I. STERN, Assz'smn Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3,241,443 March 22, 196

Harold E. Rosenberger It is hereby Certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

R9 (FI+FH+FHI+PIV) line 49, in the table heading of the third column thereof, for "u" read v column 3, line 39,

in the table, in the heading to the third column thereof, for

"n" read v columns 3 and 4, line 49, in the table, in th heading to the seventh column thereof, for "u" read v column 4, line 64, in the table in the heading to the third column thereof, for "u" read v column 6, line 2, in the table, in the heading to the third column thereof, for p read v Signed and sealed this 12th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patent 

1. AN OPTICAL SYSTEM FOR A MICROSCOPE HAVING A NUMERICAL APERTURE OF .12 AND A MAGNIFICATION OF SUBSTANTIALLY 100X AND BEING CORRECTED FOR CHROMATIC AND SPHERICAL ABERRATION, COMA AND ASTIGMATISM, SAID SYSTEM CONSISTING OF FOUR OPTICALLY ALIGNED PLANO-CONVEX LENSES NUMBERED SUCCESSIVELY 1 TO IV, LENSES I, III AND IV BENG SINGLETS AND LENS II BEING A DOUBLET, LENSES U AND II HAVING THEIR PLANO SIDES FACING TOWARD THE FRONT AND LENSES III AND IV HAVING THEIR PLANO SIES FACINGA REARWARDLY, LENS I BEING SPACED AT AN OBJECT DISTANCE S1 REARWARDLY OF A SPECIMEN SURFACE AND JOINTLY WITH LENSES II AND III FORMING AN IMAGE OF SAID SPECIMEN IN A REARWARD EYEPIECE DIAPHRAGM, LENSES I AND II BEING SEPARATED BY AN AXIAL DISTANCE DESIGNATED SI, LENSES II AND III BEING SEPARATED BY AN AIR NATED S3, AND LENSES III AND IV BEING SEPARATED BY AN AIR SPACE DESIGNATED S4, AND SAID DIAPHRAGM BEING LOCATED AT AN AXIAL DISTANCE DESIGNATED S5 FORWARDLY OF LENS, IV, THE CONSTRUCTIONAL DATA FOR SAID SYSTEM OF LENS IV, THE TABLE OF MATHEMATICAL EXPRESSIONS HEREBELOW WHEREIN THE AIR SPACES S1 TO S5 ARE DESIGNATED AS HEREABOVE FI TO FIV DESIGNATED TO FOCAL LENGTHS OF THE SUCCESSIVE LENS I TO IV, R1 TO R9 DESIGNATED TO RADII OF THE SUCCESSIVE LENS SURFACES NUMBERING FROM THE FRONT OF THE SYSTEM, THE MINUS (-) SIGN USE THEREWITH BEING APPLIED TO ANY LENS SURFACE HAVING A CENTER OF CURVATURE LYING ON THE OBJECT SIDE OF THE VERTEX OF THE SURFACE, THE THICKNESS OF THE SUCCESSIVE LENSES ARE DESIGNATED T1 TO T4, THE REFRACTIVE INDEX AND ABBE NUMBER OF THE GLASS IN SAID LENSES BEING DESIGNATED ND AND V RESPECTIVELY, AND THE COMBINED FOCAL LENGTH OF LENSES I TO II BEING DESIGNATED F, 1.43F<F1<U.58F 2.18F<FII<2.41F 3.52F<FIII<3.90F 2.39F<FIV<2.65F R1<$(F1+FII+FIII+FIV) .749F<-R2<.828F R3<$(FI+FII+FIII+FIV) .749F<R4<.828F .749F<-R5<.828F 1.84F<R6<2.04F R7<$(FI+FII+FIII+FIV) 1.25F*R8<1.38F R9<$(F1+FII+FIII+FIV) 178F<DT1<.196F .238F<T2<.263F .368F<T3<.406F .238F<T4<.263F .784F<S1<.866F .119F<S2<.131F 9,38F<S3<10.4F 2.88F<S4<3.18F 2.39F<S5<2.65F 